The ultimate goal of this project is to elucidate the mechanisms of androgen action in male reproductive function and determine the biochemical events linking the regulatory mechanisms of androgens and peptide hormones, specifically, the actions of androgens and FSH in the Sertoli cell of testis. Within this grant period we will identify properties of the androgen receptor which are of importance in relation to receptor nuclear interactions and the stimulation of gene activity. In addition to our studies on receptor stability and possible allosteric effects of other steroids, the differences between cytoplasmic and nuclear forms of the receptor will be explored with respect to subunit forms, charge and androgen binding properties, nuclear uptake and intranuclear binding. It will be established whether organ differences in subunit forms of cytoplasmic and nuclear androgen receptors reflect organ specific mechanisms regulating nuclear uptake or binding. Studies on testosterone- and dihydrotestosterone-bound receptors will be carried out to discover how these androgens affect receptor interactions within the nucleus. The role of the nuclear membrane in receptor-androgen uptake will be of particular interest. Also, we will apply new approaches to fractionating nuclei in search for receptor interaction sites. How androgens and FSH control Sertoli cell function will be studied in vivo using at least two molecular probes: the androgen binding protein ABP and the recently identified 9S androgen binder. We will identify and purify other testicular or epididymal proteins which appear useful in delineating hormonal mechanisms of other cell types in these tissues as well. Proteins will be purified and used to develop immunological methods for sensitive quantitation of changes in their concentrations in response to hormonal changes. In differentiating the effects of steroids and peptide hormones, we will avoid the artificial conditions imposed by hypophysectomy. Rather, we will selectively remove only FSH or LH and androgen from intact rats by injecting specific antisera. Attempts will be made to determine whether androgen enhancement of FSH action is mediated by a cyclic nucleotide related step or a more general effect of androgen on the protein synthesizing $ machinery of the Sertoli cell.